Pressure relief of a flange connection in overflow lines between a live steam valve and a high-pressure steam turbine inlet

ABSTRACT

A steam turbine ( 1 ) having an upper housing part ( 4 ) and a lower housing part ( 5 ), in which the steam turbine ( 1 ) has at least one overflow line ( 18 ) between a live steam adjusting valve ( 8, 9 ) and a high-pressure steam turbine inlet, and the valve housing ( 14 ) of the live steam adjusting valve ( 8, 9 ) communicates with the overflow line ( 18 ) via a flange connection ( 27 ), and a live steam pipe ( 25 ) in the live steam adjusting valve ( 8, 9 ) is provided as a steam duct between the valve housing ( 14 ) and the overflow line ( 18 ), and a sealing element ( 19 ) is disposed between the live steam pipe ( 25 ) and a sealing seat ( 28 ) in the overflow line ( 18 ), is distinguished in that an annular chamber ( 24 ) between the live steam pipe ( 25 ) and the valve housing ( 14 ) is provided with a pressure relief line ( 21 ) into a chamber of lower pressure than the live steam pressure. As a result, an improved steam turbine with pressure relief of flanges in overflow lines between live steam adjusting valves and high-pressure steam turbine inlets is made available, and as a result the flange connections are lighter in weight and embodied with greater thermal elasticity.

FIELD OF THE INVENTION

The present invention relates to a steam turbine having an upper housing part and a lower housing part, in which the steam turbine has at least one overflow line between a live steam adjusting valve and a high-pressure steam turbine inlet, and the valve housing of the live steam adjusting valve communicates with the overflow line via a flange connection, and a live steam pipe in the live steam adjusting valve is provided as a steam duct between the valve housing and the overflow line, and a sealing element is disposed between the live steam pipe and a sealing seat in the overflow line.

From the prior art, steam turbines are known which have an upper and a lower housing part. To make for easier assembly and disassembly, the valves, or more precisely live steam adjusting valves or live steam overload valves, are secured directly to the upper housing part of the turbine.

In such steam turbines, overflow lines are provided between the live steam adjusting valve or the live steam overload valve and the high-pressure steam turbine inlet. Such overflow lines are provided with flange connections or pipe couplings. In the versions with a flange or pipe couplings, steam leakage often occurs when live steam values are high, that is, at a high temperature or high pressure in non-steady-state operation. The tightness of the flanges or pipe couplings is therefore a problem in many steam turbine systems.

For solving this problem, European Patent Disclosure EP 0128343 B1 presented a steam turbine of modular construction with intermediate superheaters and in which the live steam turbine valve is a component of the outside housing of the turbine. The valve housing is mounted directly on the outside housing of the turbine by means of a flange. The diffusor in the valve is used as a steam duct between the valve housing and the turbine housing. The flange between the outside turbine housing and the valve housing is subjected in this case only to the high exhaust steam pressure and to forces of pipe reactions. Although in this case the aforementioned sealing problems are largely avoided, nevertheless here as well the flange connection is very heavy and has hardly any thermal elasticity, since in some cases it is loaded for instance with a live steam pressure of 250 bar, at rated widths of 300 mm to 350 mm.

SUMMARY OF THE INVENTION

It is therefore the object of the invention to make an improved steam turbine available with pressure relief of flanges in overflow lines between the live steam adjusting valves and the high-pressure steam turbine inlet, which avoids the aforementioned disadvantages of the prior art. Moreover, the flange should be capable of being designed as lighter in weight and made with greater thermal elasticity.

This object is attained by the characteristics of claim 1. Further advantageous features and refinements of the invention are defined by the dependent claims.

This object is attained by the invention in that the annular chamber between the live steam pipe and the valve housing is provided with a pressure relief line into a chamber of lower pressure than the live steam pressure. As a result, an improved steam turbine with pressure relief of flanges in overflow lines between live steam adjusting valves and high-pressure steam turbine inlets is made available, and as a result the flange connections are lighter in weight and embodied with greater thermal elasticity. The danger of leaks of steam to the outside in non-steady-state operation can be effectively minimized. Moreover, pressure-relieved flange connections in the region of the valve housing and overflow line can be retrofitted in existing steam turbines by being exchanged for worn valves. The lower-pressure chamber may for instance be the surrounding environment, a heat exchanger, or any other suitable place. By means of the flange connection between the live steam adjusting valve and the overflow line, the high-pressure upper part can easily be removed in an inspection.

One advantageous embodiment of the present invention provides that the pressure relief line communicates with the exhaust steam of the high-pressure turbine. Its communication with other chambers at a lower pressure level is equally conceivable.

Another advantageous embodiment of the present invention provides that the sealing elements are embodied as piston rings. These sealing elements are especially temperature- and pressure-resistant and withstand even non-steady loads.

Another advantageous embodiment of the present invention provides that the pressure relief line is embodied in the flange connection. A connection with the high-pressure exhaust steam can then be integrally formed on in a simple, uninterfering way.

A further advantageous embodiment of the present invention provides that the pressure relief line is provided for a valve housing with an inserted diffusor. In that case, in one component, the diffusor forms both the valve seat and the live steam pipe.

A further advantageous embodiment of the present invention provides that the pressure relief line is provided for a valve housing with a diffusor and a bell. In this embodiment, the diffusor and the live steam pipe are separate from one another.

A further advantageous embodiment of the present invention provides that the flange connection is designed for a temperature difference of 500° C. to 700° C., preferably for a temperature difference of 550° C. to 600° C. As a result, the invention can be provided by retrofitting existing steam turbines.

A further advantageous embodiment of the present invention provides that the flange connection is designed for a temperature difference greater than or equal to 700° C. In particular, in this case the lesser pressure loads in the non-steady-state range make themselves advantageously notable for designing the flange connection for steam turbines with high-temperature materials.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantageous embodiments of the invention are described below in conjunction with the accompanying drawings. Shown in them are:

FIG. 1, a schematic elevation view of an example of a steam turbine of the present invention;

FIG. 2, a schematic longitudinal section in the region of the live steam valve and overflow line of a first advantageous embodiment of the present invention;

FIG. 3, a schematic view, partly in section, of a second advantageous embodiment of the present invention;

FIG. 4, a schematic view, partly in section, of a third advantageous embodiment of the present invention.

Only those elements essential to comprehension of the invention are shown. In the ensuing description, elements that are the same or similar are identified by the same reference numerals.

MODES OF EMBODIMENT OF THE INVENTION

FIG. 1 shows a steam turbine 1, with a live steam supply represented by the arrows 2 and 3 leading into the upper housing part 4 and the lower housing part 5, respectively. The live steam, furnished by the boiler, not shown, enters at 2 and 3 into quick-closing valves 6 and 7, and when the quick-closing valves 6 and 7 are open it reaches live steam adjusting valves 8 and 9, through which whatever flow of steam is required to the steam turbine 1 can be adjusted and regulated. The adjustment and regulation of the live steam adjusting valves 8, 9 is effected by control motors 10 and 11 structurally joined to them. The quick-closing valves 6 and 7 are actuated by actuators 12 and 13, whose task is to abruptly shut off the steam supply line in an emergency. A flange connection 27 between the live steam adjusting valve 8 and an overflow line 18 is also shown, communicating with the upper housing part 4 of the steam turbine 1. For pressure relief, a pressure relief line in the flange connection 27 is provided with a connection 22 to the high-pressure exhaust steam of the steam turbine 1.

FIG. 2 is a schematic longitudinal section in the region of the valve housing and overflow line of a first advantageous embodiment of the present invention with an inserted diffusor. In this embodiment, the rotationally symmetrical valve housing 14 communicates with a likewise rotationally symmetrical overflow line 18 via a flange 16 of the valve housing, a flange 17 of the overflow line, and expansion pin screws 20. This represents the flange connection 27. The flow connection for the live steam is established by means of an integrally embodied diffusor 15 and live steam pipe 25, located inside the valve housing 14 and the overflow line 18, which is thrust from the valve housing 14 into an annular chamber 24 and is received with sealing elements 19 in a dc 28 of the overflow line. On its end toward the valve, the diffusor 15 forms a valve seat. Sealing of the end toward the overflow line of the live steam pipe 25 from leakage is effected by means of a sealing element 19, which comprises piston rings. The annular chamber 24 formed between the live steam pipe 25 and the valve housing 14 communicates with the high-pressure exhaust steam via a pressure relief line 21, which has a connection 22. The pressure relief line 21 is machined into the flange 16 of the valve housing and extends perpendicularly to the center line of the diffusor. As a result, no interfering additional protrusions are created on the component.

FIG. 3 is a schematic view, partly in section, of a second advantageous embodiment of the present invention with an inserted diffusor. The layout is in principle like that described for FIG. 2 and will therefore not be described again here. In a distinction from the embodiment of FIG. 2, here the pressure relief line 21 and the connection 22 to the high-pressure exhaust steam are located on the end of the annular chamber 24 toward the diffusor. Once again, the pressure relief line 21 extends perpendicular to the center line of the diffusor. As a result, weakening of the flange is avoided.

FIG. 4 is a schematic view, partly in section, of a third advantageous embodiment of the present invention, with a live steam pipe 25 and a bell 23. In contrast to the embodiments shown in FIGS. 2 and 3, here the live steam pipe 25 is embodied separately from the diffusor 15. The overflow line 18 and the live steam pipe 25 are embodied integrally as a so-called bell 23, in which an annular chamber 24 is also embodied. The cylindrically embodied live steam pipe 25 protrudes into the valve housing 14 via the front edge 26 of the flange 17 of the overflow line and is sealed off in the valve housing by sealing elements 19. In this exemplary embodiment, the sealing elements 19 are embodied as piston rings. The pressure relief line 21 and the connection 22 to the high-pressure exhaust steam are located on the end toward the valve housing of the annular chamber 24, slightly obliquely to the center axis of the valve housing.

During startup of the turbine, that is, in non-steady-state operation, surges and pressure- and temperature-dictated fluctuations are compensated for by changes in length in the region of the live steam valve 8 and overflow line 18. Because of the pressure relief line 21 according to the invention, the incident loads on the flange connection 27 then are minimized.

LIST OF REFERENCE NUMERALS

1 Steam turbine

2 Live steam supply

3 Live steam supply

4 Upper housing part

5 Lower housing part

6 Quick-closing valve

7 Quick-closing valve

8 Live steam adjusting valve

9 Live steam adjusting valve

10 Control motor

11 Control motor

12 Actuator

13 Actuator

14 Valve housing

15 Diffusor

16 Flange of valve housing

17 Flange of overflow line

18 Overflow line

19 Sealing element

20 Expansion pin screw

21 Pressure relief line

22 Connection to high-pressure exhaust steam

23 Bell

24 Annular chamber

25 Live steam pipe

26 Front edge of flange

27 Flange connection

28 Sealing seat

29 Exhaust steam conduit 

1. A steam turbine having an upper housing part and a lower housing part, in which the steam turbine has at least one overflow line between a live steam adjusting valve and a high-pressure steam turbine inlet, and the valve housing of the live steam adjusting valve communicates with the overflow line via a flange connection, and a live steam pipe in the live steam adjusting valve is provided as a steam duct between the valve housing and the overflow line, and a sealing element is disposed between the live steam pipe and a sealing seat in the overflow line, wherein an annular chamber between the live steam pipe and the valve housing is provided with a pressure relief line into a chamber of lower pressure than the live steam pressure.
 2. The steam turbine of claim 1, wherein the pressure relief line communicates with an exhaust steam conduit of the high-pressure turbine.
 3. The steam turbine of claim 1, wherein the sealing elements are embodied as piston rings.
 4. The steam turbine of claim 1, wherein the pressure relief line is embodied in the flange connection.
 5. The steam turbine of claim 1, wherein the pressure relief line is provided for a valve housing with an inserted diffusor.
 6. The steam turbine of claim 1, wherein the pressure relief line is provided for a valve housing with a diffusor and a bell.
 7. The steam turbine of claim 1, wherein the flange connection is designed for a temperature difference of 500° C. to 700° C., preferably for a temperature difference of 550° C. to 600° C.
 8. The steam turbine of claim 1, wherein the flange connection is designed for a temperature difference greater than or equal to 700° C. 